Full color OLED and method of fabricating the same

ABSTRACT

A full color organic light emitting display device (OLED) and a method of fabricating the same are provided. The OLED includes an element substrate and an encapsulating substrate. The element substrate includes a color filter layer or a color conversion layer, as well as an organic layer with an emission layer that emits light of a single color. The encapsulating substrate includes a color filter or a color conversion layer and a moisture absorbent, and a the color filter or color conversion layer corresponds to the emission region. Accordingly, there is no need to have a separate process for the moisture absorbent and the color filter layer or the color conversion layer may be formed without using a shadow mask, so that a high resolution OLED may be advantageously realized.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2004-0094358, filed Nov. 17, 2004, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a full color organic light emittingdisplay device (OLED) and a method of fabricating the same, and moreparticularly, to a full color dual emission OLED having a colorconversion layer or a color filter layer with a moisture absorbent on anencapsulating substrate and a method of fabricating the same.

2. Discussion of the Background

Generally, an OLED includes a substrate, an anode arranged on thesubstrate, an emission layer (EML) arranged on the anode, a cathodearranged on the EML, and an encapsulating substrate. In such an OLED,applying a voltage between the anode and the cathode injects holes andelectrons into the EML. The holes and electrons then recombine in theEML to generate excitons, which emit light when transitioning from anexcited state to a ground state.

In order to realize a full color OLED, emission layers corresponding torespective red (R), green (G), and blue (B) light may be formed.However, the emission layers that emit R, G, and B light, respectively,have different lifetime characteristics. Hence, it may be difficult tomaintain white balance over long periods of time, and there is alimitation in patterning each pixel so that a high-resolution displaydevice may not be advantageously realized.

To cope with this problem, a method that includes forming an emissionlayer that emits a single color of light has been proposed. The methodfurther includes forming a color filter layer for extracting lightcorresponding to a predetermined color from the light emitted from theemission layer, or forming a color conversion layer for converting thelight emitted from the emission layer into light of a predeterminedcolor. As an example thereof, U.S. Pat. No. 6,515,418 discloses anactive matrix OLED including an emission layer that emits white lightand a color filter layer formed by photolithography. Furthermore, U.S.Pat. No. 6,522,066 discloses an active matrix OLED including an emissionlayer that emits blue light and a color filter layer formed byphotolithography.

An encapsulating substrate for protecting an anode, an emission layer,and a cathode is attached to the substrate. The emission layer is apt tobe affected by moisture and oxygen, so that a moisture absorbent may bedisadvantageously attached thereto after forming a separate region formounting the moisture absorbent within the encapsulating substrate.

SUMMARY OF THE INVENTION

The present invention provides a full color OLED and a method offabricating the same, with a color filter layer or a color conversionlayer on an element substrate and with a color conversion layer or acolor filter layer and a moisture absorbent on an encapsulatingsubstrate such that alignment may be facilitated at the time ofencapsulation and a high-resolution display device may be advantageouslyrealized.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

The present invention discloses a full color organic light emittingdisplay device including an element substrate and an encapsulatingsubstrate. The element substrate includes a pixel electrode, an organiclayer having at least an emission layer, and a counter electrode, andthe encapsulating substrate is coupled with the element substrate.Either a first color filter layer or a first color conversion layer isarranged on the element substrate, the emission layer emits light of asingle color, and either a second color filter layer or a second colorconversion layer has a moisture absorbent and is arranged on theencapsulating substrate to correspond to the emission layer.

The present invention also discloses a method of fabricating a fullcolor organic light emitting display device including forming either afirst color filter layer or a first color conversion layer on an elementsubstrate, forming a pixel electrode on the element substrate, formingan organic layer including at least an emission layer on the pixelelectrode, forming a counter electrode on the organic layer, and formingeither a second color filter layer or a second color conversion layerhaving a moisture absorbent on an encapsulating substrate correspondingto the element substrate.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a cross-sectional view of a full color OLED in accordance withan exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a full color OLED in accordance withanother exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure is thorough, and will fully convey the scope of theinvention to those skilled in the art. In the drawings, the size andrelative sizes of layers and regions may be exaggerated for clarity.

It will be understood that when an element such as a layer, film, regionor substrate is referred to as being “on” another element, it can bedirectly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present.

FIG. 1 is a cross-sectional view of a full color OLED in accordance withan exemplary embodiment of the present invention. Referring to FIG. 1,the OLED includes an element substrate 100 and an encapsulatingsubstrate 300. The element substrate 100 includes first color filterlayers or color conversion layers (“first color filter/conversionlayers”) 710, 720, and 730 on one surface thereof, a thin filmtransistor including a gate electrode 132 and source and drainelectrodes 150 and 152 on its rear surface, a pixel electrode 180coupled with either the source or drain electrode 150 or 152, an organicemission layer 190 arranged on the pixel electrode 180, and a counterelectrode 200. The encapsulating substrate 300 includes second colorfilter layers or color conversion layers (“second colorfilter/conversion layers”) 410, 420, and 430, which have a moistureabsorbent 500 and correspond to the organic emission layer 190.

In this case, the first color filter/conversion layers 710, 720, and 730formed on the element substrate 100 correspond to the organic emissionlayer 190. The first color filter/conversion layers 710, 720, and 730may be formed anywhere between the element substrate 100 and the organicemission layer 190. When the first color filter/conversion layers 710,720, and 730 are formed on the element substrate 100, a separatepassivation layer may be formed thereon to prevent the first colorfilter/conversion layers 710, 720, and 730 from being damaged.

The organic emission layer 190 emits a single color light such as blueor white light, and the second color filter/conversion layers 410, 420,and 430 provide red, green, and blue light, respectively, from the lightemitted from the organic emission layer 190.

The moisture absorbent 500 may be arranged on the second colorfilter/conversion layers 410, 420, and 430, or it may be formed on theentire surface of the encapsulating substrate 300 including the secondcolor filter/conversion layers 410, 420, and 430. Alternatively, as FIG.2 shows, color filter/conversion layers 610, 620, and 630 may be formedincluding the moisture absorbent.

The color filter layers 410, 420, 430, 710, 720, and 730 may includepigment and high molecular binder, and they may be classified into redcolor filter layers 410 and 710, green color filter layers 420 and 720,and blue color filter layers 430 and 730 depending on the kind ofpigment. The red color filter layers 410 and 710, the green color filterlayers 420 and 720, and the blue color filter layers 430 and 730 allowlight incident from the emission layer to be transmitted by a wavelengthof red region, a wavelength of green region, and a wavelength of blueregion, respectively.

The color filter layers 410, 420, 430, 710, 720, and 730 may be formedby a laser induced thermal imaging (LITI) method. When using the LITImethod, a donor film for forming the color filter layers 410, 420, 430,710, 720, and 730 is prepared by forming a light-heat conversion layeron a base film and forming a transfer layer for the color filter layeron the light-heat conversion layer. The donor film may then be arrangedon the encapsulating substrate such that the transfer layer for thecolor filter layer faces the encapsulating substrate, and a laser isirradiated on the base film of the donor film to transfer the transferlayer for the color filter layer onto the encapsulating substrate,thereby forming the color filter layers 410, 420, 430, 710, 720, and730. By doing so, the red color filter layers 410 and 710, the greencolor filter layers 420 and 720, and the blue color filter layers 430and 730 may be formed on the encapsulating substrate, respectively.Alternatively, the color filter layers 410, 420, 430, 710, 720, and 730may be formed by a photolithography method of repeatedly carrying outexposure and development or by an inkjet method. When forming the colorfilter layers 410, 420, 430, 710, 720, and 730 with the inkjet method, abarrier may be formed between the color filter layers to prevent thecolor filters from interfering with each other and color mixing fromoccurring. Additionally, the barrier prevents an emission portion frombeing damaged due to external pressure.

The color conversion layers 410, 420, 430, 710, 720, and 730 may includea fluorescent material and a high molecular binder. The fluorescentmaterial is excited by light incident from the emission layer, and as ittransitions to a ground state, it emits light having a longer wavelengththan the incident light. The fluorescent material is classified into redcolor conversion layers 410 and 710 for converting incident light intored light, green color conversion layers 420 and 720 for convertingincident light into green light, and blue color conversion layers 430and 730 for converting incident light into blue light, depending on thekind of the fluorescent material.

Like the color filter layers 410, 420, 430, 710, 720, and 730, the colorconversion layers 410, 420, 430, 710, 720, and 730 may also be formed bya LITI method, a photolithography method, or an inkjet method. In thiscase, when forming the color conversion layers 410, 420, 430, 710, 720,and 730 by the LITI method, the same method as that of forming the colorfilter layers may be applied except that a transfer layer for the colorconversion layer is formed on the base film. Additionally, when formingthe color conversion layers 410, 420, 430, 710, 720, and 730 by theinkjet method, a barrier is formed between the color conversion layers.

Furthermore, color filter/conversion layers 610, 620, and 630 includinga moisture absorbent may be formed as described above.

The organic emission layer 190 may be formed of at least two organicthin films, which may emit light having different wavelengths in orderto emit a single color light. Additionally, the emission layer may beformed of a high molecular weight material and/or a low molecular weightmaterial, and it may be formed on the entire surface of the substrate byspin coating or vacuum deposition.

The organic emission layer 190 preferably emits white light when thecolor filter layers are formed and blue light when the color conversionlayers are formed.

Hereinafter, a method of fabricating the full color OLED according to anexemplary embodiment of the present invention will be described withreference to FIG. 1 and FIG. 2.

First color filter/conversion layers 710, 720, and 730 are formed on onesurface of the element substrate 100, which has red (A), green (B), andblue (C) pixel regions. In this case, the color filter/conversion layers710, 720, and 730 may be formed by a LITI method, a photolithographymethod, or an inkjet method, and a barrier may be formed between thecolor filter/conversion layers 710, 720, and 730 when they are formed bythe inkjet method. Alternatively, the first color filter/conversionlayers 710, 720, and 730 may be formed anywhere between the elementsubstrate 100 and the organic emission layer 190. For example, they maybe formed between the organic emission layer 190 and the pixel electrode180, or between the pixel electrode 180 and a planarization layer 170.When the first color filter/conversion layers 710, 720, and 730 areformed on one surface of the element substrate 100, a passivation layer,(not shown) which protects the first color filter/conversion layers 710,720, and 730, may be further formed on the element substrate 100including the first color filter/conversion layers 710, 720, and 730.

A buffer layer 110 of a predetermined thickness may then be formed on arear surface of the element substrate 100. The buffer layer 110 preventsimpurities from the element substrate 100 from flowing into asubsequently formed thin film transistor.

Polycrystalline silicon layer patterns 120 may then be formed on thebuffer layer 110, and impurities may be implanted into both sides of thepolycrystalline silicon layer patterns 120 to form source regions 122and drain regions 124 in the respective pixel regions A, B, and C. Inthis case, a channel region 126 is formed between the source region 122and the drain region 124.

A gate insulating layer 130 may be formed on the entire surface of theresultant structure, and gate electrodes 132 may be formed to correspondto the channel regions 126 of the polycrystalline silicon layer patterns120.

An interlayer-insulating layer 140 may then be formed on the entiresurface of the resultant structure and etched to form contact holes 142,which expose the source and drain regions 122 and 124. Subsequently,source and drain electrodes 150 and 152 are formed coupled with thesource and drain regions 122 and 124, respectively, via the contactholes 142.

A passivation layer 160 and a planarization layer 170 may then be formedon the entire surface of the resultant structure.

The passivation layer 160 and the planarization layer 170 may be etchedto form via holes 172, which expose the drain electrodes 152.

Subsequently, pixel electrodes 180, which are coupled with the drainelectrodes 152 through the via holes 172, may be formed in the pixelregions A, B, and C. Here, the pixel electrode 180 is preferably atransparent electrode.

A portion of the pixel electrode 180 is then exposed to form a pixeldefining layer pattern 182 defining an emission region on the entiresurface of the resultant structure.

An organic layer 190, which includes at least an emission layer, and acounter electrode 200 may then be formed on the entire surface of theresultant structure. In this case, the organic layer 190 includes anemission layer that emits blue or white light, and the counter electrode200 is a transparent electrode or a translucent electrode.

A transparent passivation layer (not shown) may then be formed on thecounter electrode 200.

Subsequently, an encapsulating substrate 300, which corresponds to theelement substrate 100, is prepared. Here, the encapsulating substrate300 is preferably transparent.

Second color filter/conversion layers 410, 420, and 430 are formed onthe encapsulating substrate 300, that is, a portion corresponding to theemission region of the element substrate 100. When the emission layeremits white light, color filter layers may be formed on theencapsulating substrate 300. On the other hand, when the emission layeremits blue light, color conversion layers may be formed on theencapsulating substrate 300. In this case, when the emission layer emitsblue light, the color conversion layers need not be formed in the bluecolor pixel region (C) of the encapsulating substrate 300. The secondcolor filter/conversion layers 410, 420, and 430 may be formed by a LITImethod, a photolithography method, or an inkjet method. A barrier may beformed between the second color filter/conversion layers when they areformed by the inkjet method.

A moisture absorbent 500 may be formed on the second colorfilter/conversion layers 410, 420, and 430, or on the entire surface ofthe encapsulating substrate 300 including the second colorfilter/conversion layers 410, 420, and 430.

The moisture absorbent 500 includes a component that is capable ofabsorbing moisture and oxygen, and it is formed of a transparentmaterial. For example, the moisture absorbent 500 may include a nanoparticle moisture absorbent having SiO₂ as its main component, achemical reactive moisture absorbent having CaO dispersoid as its maincomponent, a nano particle/chemical reactive moisture absorbent havingSiO₂ and CaCl₂ as its main component, and an organic-inorganic moistureabsorbent having an organic-inorganic composite moisture absorbent asits main component.

Alternatively, the moisture absorbent may be a transparent material thatis mixed with the color filter/conversion layers 610, 620, and 630, asshown in FIG. 2.

Table 1 shows the main component, test cell acceleration storagelifetime, and formation method of the moisture absorbent. TABLE 1 Testcell acceleration storage Coating Main component lifetime (hr) methodNano particle SiO₂ 75 Screen moisture absorbent printing Nano particle/SiO₂ + CaCl₂ 168 Screen chemical reactive printing moisture absorbentChemical reactive CaO dispersoid 560 Spray moisture absorbent coatingOrganic-inorganic Organic-inorganic 400 Screen moisture absorbentcomposite moisture printing absorbent

The moisture absorbent 500 may be formed on the surface of the secondcolor filter/conversion layers 410, 420, and 430 of the encapsulatingsubstrate 300 as described above, so that a separate space for mountingthe moisture absorbent 500 is not required and physical damages of thesecond color filter/conversion layers 410, 420, and 430 may beprevented.

According to exemplary embodiments of the present invention as describedabove, a color filter layer or a color conversion layer may be formed onthe encapsulating substrate, and a moisture absorbent may be formed onthe color filter layer or the color conversion layer, or the colorfilter layer or the color conversion layer may be formed containing themoisture absorbent, so that a process thereof may be simplified withoutaffecting optical characteristics and a high resolution display devicemay be advantageously realized.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A full color organic light emitting display device (OLED),comprising: an element substrate including a pixel electrode, an organiclayer comprising an emission layer, and a counter electrode; anencapsulating substrate coupled with the element substrate; either afirst color filter layer or a first color conversion layer arranged onthe element substrate; and either a second color filter layer or asecond color conversion layer having a moisture absorbent and arrangedon the encapsulating substrate to correspond to the emission layer,wherein the emission layer emits light of a single color.
 2. The OLED ofclaim 1, further comprising: a thin film transistor arranged between theelement substrate and the pixel electrode and electrically coupled withthe pixel electrode.
 3. The OLED of claim 1, wherein the pixel electrodeand the counter electrode are transparent electrodes.
 4. The OLED ofclaim 1, wherein the first color filter layer is arranged on the elementsubstrate, the second color filter layer is arranged on theencapsulating substrate, and the emission layer emits white light. 5.The OLED of claim 1, wherein the first color conversion layer isarranged on the element substrate, the second color conversion layer isarranged on the encapsulating substrate, and the emission layer emitsblue light.
 6. The OLED of claim 1, wherein the moisture absorbentcomprises a transparent material.
 7. The OLED of claim 1, wherein themoisture absorbent comprises at least one moisture absorbent selectedfrom the group consisting of a nano particle moisture absorbent, achemical reactive moisture absorbent, and an organic-inorganic moistureabsorbent.
 8. The OLED of claim 1, wherein the moisture absorbent isarranged on an entire surface of the encapsulating substrate includingeither the second color filter layer or the second color conversionlayer.
 9. The OLED of claim 1, wherein the moisture absorbent isincluded within either the second color conversion layer or the secondcolor filter layer.
 10. The OLED of claim 1, further comprising: abarrier arranged between color filter layers or between color conversionlayers.
 11. The OLED of claim 1, further comprising: a passivation layercovering either the first color filter layer or the first colorconversion layer.
 12. The OLED of claim 1, wherein either the firstcolor filter layer or the first color conversion layer is arrangeddirectly on a first side of the element substrate, the pixel electrodeis arranged on a second side of the element substrate, and the firstside differs from the second side.
 13. A method of fabricating a fullcolor organic light emitting display device (OLED), comprising: formingeither a first color filter layer or a first color conversion layer onan element substrate; forming a pixel electrode on the elementsubstrate; forming an organic layer including at least an emission layeron the pixel electrode; forming a counter electrode on the organiclayer; and forming either a second color filter layer or a second colorconversion layer having a moisture absorbent on an encapsulatingsubstrate corresponding to the element substrate.
 14. The method ofclaim 13, further comprising: forming at least one thin film transistorbetween the element substrate and the pixel electrode.
 15. The method ofclaim 13, wherein the pixel electrode and the counter electrode aretransparent electrodes.
 16. The method of claim 13, wherein the firstcolor filter layer is formed on the element substrate and the secondcolor filter layer is formed on the encapsulating substrate when theemission layer emits white light.
 17. The method of claim 13, whereinthe first color conversion layer is formed on the element substrate andthe second color conversion layer is formed on the encapsulatingsubstrate when the emission layer emits blue light.
 18. The method ofclaim 13, wherein the organic layer comprises an emission layer emittingeither white or blue light.
 19. The method of claim 18, wherein thefirst color filter layer is formed on the element substrate and thesecond color filter layer is formed on the encapsulating substrate whenthe emission layer emits white light.
 20. The method of claim 18,wherein the first color conversion layer is formed on the elementsubstrate and the second color conversion layer is formed on theencapsulating substrate when the emission layer emits blue light. 21.The method of claim 13, wherein the color filter layers or the colorconversion layers are formed by a laser induced thermal imaging method,a photolithography method, or an inkjet method.
 22. The method of claim21, further comprising: forming a barrier between the color filterlayers or the color conversion layers when the color filter layers orthe color conversion layers are formed by the inkjet method.
 23. Themethod of claim 13, wherein the moisture absorbent comprises atransparent material.
 24. The method of claim 23, wherein the moistureabsorbent comprises at least one moisture absorbent selected from thegroup consisting of a nano particle moisture absorbent, a chemicalreactive moisture absorbent, and an organic-inorganic moistureabsorbent.
 25. The method of claim 13, wherein the moisture absorbent isformed by a screen printing method or a spray coating method.
 26. Themethod of claim 13, wherein the moisture absorbent is formed on anentire surface of the encapsulating substrate including either thesecond color filter layer or the second color conversion layer.
 27. Themethod of claim 13, wherein either the second color filter layer or thesecond the color conversion layer is mixed with the moisture absorbentto be formed in one body.
 28. The method of claim 13, wherein themoisture absorbent is formed on either the second color filter layer orthe second color conversion layer.
 29. The method of claim 13, furthercomprising: forming a passivation layer covering either the first colorfilter layer or the first color conversion layer.
 30. The method ofclaim 13, wherein either the first color filter layer or the first colorconversion layer is formed directly on a first side of the elementsubstrate, the pixel electrode is formed on a second side of the elementsubstrate, and the first side differs from the second side.